The human primary somatosensory cortex corresponds to an organized topological map of all body parts (somatotopy). However, the representative proportion of body parts in the brain differs from that of the physical body. This distorted representation is called the cortical homunculus. Body parts with extensive cortical representation have a greater sensitivity in spatial resolution. We have developed the software, Face Homunculus Viewer, that can modify any facial images to homunculus-like faces with sensitivity parameters. The software was employed to support children and adults in understanding the cortical homunculus and the sensitivity differences of various body parts. Several workshops were held in which participants measured two-point discrimination thresholds at the forearm, lip and forehead to create a personalized homunculus. The software may contribute to user knowledge on the mechanisms of somatosensory perception in the brain of humans through their own embodied experience.
Galvanic Tongue Stimulation is the technology which can enhances the taste sensation. Our previous study has already demonstrated that repetitive square current stimulation enhances salty and umami taste induced by NaCl and glutamic sodium water solution during stimulation. However, it is not clear whether the repetitive square current stimulation is effective or not in other three basic taste i.e., sweetness, sourness, and bitterness. The aim of this paper is to demonstrate that repetitive square current stimulation enhances all five basic tastes induced by electrolyte water solutions with psychological method adhering to our previous works.
Recently, many interactive video display devices using body movement as input have been developed. However, their intrinsic latency before the resulting images are displayed creates a discrepancy between the visual information to the user and the physical sensation. This research aims to investigate the impact on user performance and latency perception when there is latency between the user's physical input to the system and the visual feedback. We developed a video latency control system to film the user's hand movements and control the latency when displaying the video (The standard deviation is 0.38 ms). The minimum latency of the system is 4.3 ms, hence this enables us to investigate the performance and latency perception in unknown low latency range. Using this system, we conducted experiments wherein 20 subjects performed a pointing task based on Fitts' law to clarify the effect of video latency, particularly for low latency. Experimental results showed that when the latency is over 24.3 ms, it begins to be sensed more easily by the user and the performance begins to decrease. This result will be applied to determine a standard limit for video latency in interactive video devices.
The aim of this paper is to analyze the mixing effect of linear vection (LV) and circular vection (CV) when perceiving both of them. Vection is a visual induced self-motion illusion caused by observing a moving pattern in certain direction. And it is classified with two types LV and CV by their moving direction; LV is rectilinear motion sense, and CV is rotational motion sense. Most studies focus on either LV or CV. Therefore, in this paper, we focused on both rectilinear and rotational directions and analyzed the relationship between LV and CV. Through the experiments where rectilinear and rotational visual stimulus coexist, we found that LV and CV strength are in a negative correlation, and the vection strength is obtained as vector sum of LV and CV strength measured under each condition.
Smoothness is one of the important factors in controlling texture sensation in tactile VR. In previous research, we created the feeling of smoothness by utilizing Velvet Hand Illusion (VHI) which is one tactile illusion phenomenon. We adopted a dot-matrix display as a haptic device to clarify that VHI can be created in the dot-matrix display with the two parallel moving lines formed by the stimulus pins. From this result, it was clarified that we can perceive apparent motion in tactile sensation as well as visual sensation. In our more recent research we focus on the tactile Gestalt which consists of the two parallel moving lines. The tactile Gestalt is different from the visual Gestalt because we can recognize not only shapes such as a letter and a figure, but also smoothness in the tactile Gestalt. Since the dot-matrix display can create various dot patterns, it is possible to clarify the condition of the tactile Gestalt to generate VHI feeling. Therefore, in this research, we aim to clarify the basic characteristics of tactile Gestalt using the dot-matrix display. We investigate the relationship between the pins distance forming a line and VHI occurrence, and the absolute threshold of line length which is the trigger to generate VHI. As a result, the threshold of the distance between pins forming the line coincides with two point threshold of the palm. Also, the absolute threshold of the parallel line length is about 28 mm.
In the tactile presentation by wind and air flow, it is possible to present a sense in a non-contact manner. They can be presented simultaneously with other sensations such as visual sense and auditory sense, so that the presence can be further enhanced. Therefore, we have been exploring the possibility of optimal wind direction presentation by measuring the property of wind direction perception. In the previous study, we have been targeting the frontal region of the head. In this paper, we performed the wind direction perception test on the rear and lateral region of the head for each gender and compared the results. The results demonstrate that it is difficult to discriminate wind direction at the lateral head position and when generating uniform wind. In addition, the results demonstrate that there is no significant difference between genders.
In this study, we examined whether the proprioceptive drift depends on (1) direction of the synchronous hand movement (horizontal or back-and-forth), (2) direction of the positional shift of virtual hand (left/right or near/far), (3) the congruency of the direction of the shift and the movement, and (4) perspective cue in the back-and-forth movement. Results showed that the visual feedback of synchronous horizontal retinal motion of participant's own hand did not cause larger proprioceptive drift than the synchronous change of disparity and size by back-and-forth movement, while the near/far shift of one's own hand showed smaller drift than the left/right shift. Besides, there was no enhancement of the drift when the direction of these factors is congruent, although the hand movement may induce more attention to the moving direction. These results suggest that the synchronous motion itself is an important factor on the drift, irrespective of horizontal or back-and-forth direction and the congruency of size change and the direction of the displacement causes significantly different effect on the drift.
Visual and auditory senses are mainly used as sensory information in VR contents. In addition to these senses, we consider olfactory and haptic senses together aiming at better quality of VR contents. We created such VR contents and did evaluation experiment. We provided smell using olfactory display using solenoid valves with high speed switching and haptic sense using wire driven haptic display. In experiment, we added olfactory and/or haptic sense to visual/audio senses and tested whether user perception changes according to the provided sense. As a result, we found that a user's sensation was enhanced after adding olfactory and haptic information to visual/audio information.
Many studies have reported that subjective taste intensity is enhanced by odors which are congruent, for example a sweet taste and a vanilla odor. Some reports have suggested that subjective taste is more strongly enhanced by retronasal than by orthonasal odors; others have suggested that taste enhancements by both odor routes are identical. Differences between the two routes include the direction of airflow accompanying breath. Although we have already reported the enhancement of a sweet taste induced by a vanilla odor, the enhancement of a salty taste has not been reported. Here, we examined whether the enhancement of a salty taste is induced by a soy sauce odor synchronized with breathing. The results of this study, in which olfactory stimuli were presented synchronously with breathing in, demonstrate that a retronasal soy sauce odor after drinking enhanced a salty taste, but an orthonasal soy sauce odor before drinking did not.
In this study, we propose and evaluate a warmth display, which is designed to heat a part of user's hand when the part of the hand get warmth in virtual world displayed by Head Mounted Display. For the heat source, we use visible light LED because it is easily available and controllable. Arranging several LEDs around the hand, the display can warm some part of the hand. As it warms hands without contact, the heat from the display can be cut off immediately and interactive warmth presentation is possible. Moreover, we evaluated the safety, reaction time, sensation of warmth and temperature change caused by the display.
The perception of hardness is fundamental for the sense of hand, but it is difficult to render the hardness of stiff objects when the power of haptic devices is limited. There is a method of using vibration stimulus to enhance the presentable hardness of objects in a haptic device. However, this method requires high frequency response characteristics for a haptic device. Therefore, in this study, we proposed a U-shaped stylus that improves the hardness rendering ability of a haptic device by using resonance, and conducted a perceptual experiment to confirm the effect of the stylus. As a result, we clarified that the hardness rendering ability can be effectively improved by using and adjusting the resonance frequency of the U-shaped stylus.
A virtual reality system, combined with surrounding visual, auditory content and motion platform, can provide an immersive experience including a sensation of motion. However, the space and cost requirements for installation of motion platforms hinder its practical use. To overcome this issue, we have proposed to use a car as a motion platform. We tested an immersive content in which users ride on a trolley in a virtual space, on two types of automatic driving algorithms. The results showed that this system enhanced "enjoyment", "sense of fear" and "feeling of movement" of the content. Comparison of algorithms showed that "acceleration feedback" is more advantageous than "jerk feedback".
In this paper, we propose an optical system called Deco-Wall that can form mid-air images in front of building walls. This is achieved by installing optical components overhead. It displays a vertical mid-air image that is easily visible in front of the viewer. Our contributions are formulating its field of view, measuring the luminance of mid-air images formed with our system by using a luminance meter, measuring the resolution of the mid-air images by MTF, and selection of suitable materials for our system. We prototyped two applications for proof of concept and observed user reactions to evaluate our system.
Presenting realistic tactile sensation increases the reality of VR applications. However, it is difficult to realize such a device by using a single tactile stimulus (e.g. only vibration). Therefore, we developed a complex tactile presentation system that presents stimuli of force, vibration, and temperature to cutaneous receptors, and also presents a force sensation to proprioceptor, based on the Haptic Primary Color Principle. This paper describes the system configuration, the control method, and two experiments using the tactile presentation system. In the first experiment, the parameter sets were estimated for reproducing tactile texture of multiple materials, and the evaluation for a degree of similarity between display stimuli and tactile feeling of each material was conducted. In the second experiment, the evaluation for the relevance of Japanese onomatopoeia to tactile sensations, was conducted, and some onomatopoeia had strong connections with specific tactile feeling reproduced by the system. The sequence of experiments suggested that our proposed system had the ability to reproduce smooth tactile feeling, such as smooth and slippery, with relatively high fidelity; however, softness feeling, such as soft, fluffy, and mushy, was suggested relatively difficult to reproduce. Moreover, according to these findings, we estimated parameter sets of the proposed device to represent specific tactile feelings, and found that a pair of contrasting tactile feelings (e.g. smooth and rough) was reasonably located on opposite side of the tactile stimulus coordinate space from one another.
This paper reports the system visualizing bodily gestures of the user operating a surrogate robot. The conceptual core of telexistence explains that a human-like robot equipping with various substitute devices of human functions can be used as the surrogate body of human (i.e. avatar). Although a 3-DOF robot-head can provide the basic functions of telexistence, these robots have limited capacity to express bodily gestures performed by the robot's user. Here, we propose the bodily expression capacity expansion method by using virtual reality to realize remote embodied communication.